Large, 1 G-Byte chips using flash-memory technologies with electrically-erasable programmable read-only memory (EEPROM) are available. Small flash-memory cards have been designed that have a connector that can plug into a specialized reader, such as for compact-flash, secure-digital, memory stick, or other standardized formats.
Recently, flash memory cards are being sold that contain a USB connector. Such USB-flash memory cards do not require a specialized reader but can be plugged into a USB connector on a personal computer (PC) or other hosting device. These USB-flash memory cards can be used in place of floppy disks and are known as USB key drives, USB thumb drives, and a variety of other names. These USB-flash cards can have a capacity of more than ten floppy disks in an area not much larger than a large postage stamp.
FIG. 1 shows a bottom view of assembly of a male slim USB connector that is integrated with a circuit-board substrate of a flash memory card. Flash memory chip 75 may be a 128 Mega-byte non-volatile chip or may have some other capacity. Controller chip 78 contains a flash-memory controller that generates signals to access memory locations within flash memory chip 75. Controller chip 78 also contains a USB interface controller that serially transfers data to and from flash memory chip 75 over a USB connection.
A USB connector may be formed on board 60, which is a small circuit board with chips 75, 78 mounted thereon. Multi-layer printed-circuit board (PCB) technology can be used for board 60. Metal contacts carry the USB signals generated or received by controller chip 78. USB signals include power, ground, and serial differential data D+, D−.
The USB flash-memory card is assembled from PCB board 60 and its components, and lower case 65, which are sandwiched together to form the flash-memory card. The bottom surface of board 60 is visible in FIG. 1.
Flash memory chip 75 and controller chip 78 are mounted on the reverse (bottom) side of board 60, which can be a multi-layer PCB or similar substrate with wiring traces. The 4 USB contacts are formed on the top side of board 60 and are not visible in this bottom view. Since most components are mounted on the bottom side of board 60 opposite the top side with the USB metal contacts, board 60 does not need a plastic cover over its top side. This allows the flash-memory card to have a lower profile or even a co-planar top surface.
Extension 61 of board 60 has a width that approximately matches the width of the connector substrate and the metal wrap in a male USB connector, about 12.4 mm. Metal USB contacts (not visible) are formed on the top side of extension 61 to act as the USB metal contacts of the male slim USB connector. End 72 of board 60 is inserted into the female USB connector.
Lower case 65 also includes extended region 80. LED 93 can be mounted on board 60, such as on the bottom side with other components, or extending from an edge of board 60.
The width of the USB flash-memory drive may flare beyond extension 61, causing a flared or T-shape to the device. This widening of the USB flash-memory device is undesirable.
While traditional USB connectors have metal wraps around a connector substrate, USB flash-memory drives are often made from plastic housings. A USB flash-memory drive may have a metal wrap around extension 61, but a plastic housing such as lower case 65 around for the remaining portion of the USB device. Having the metal-wrapped connector with the plastic housing may be aesthetically unappealing, and the plastic housing may be less durable than the metal-wrapped USB connector. The USB device may crack and fail due to strain at the metal-plastic interface or join between the metal-wrapped USB connector and the plastic housing.
What is desired is a metal-wrapped USB flash-memory device. A USB flash-memory device with a metal cover extending from the USB connector over the plastic housing is desirable.